


The Trail

by Josh89



Category: Castle (TV 2009), Percy Jackson and the Olympians & Related Fandoms - All Media Types, Percy Jackson and the Olympians - Rick Riordan, The Heroes of Olympus - Rick Riordan
Genre: Background Case, Crossover, Don't copy to another site, F/M, Not Canon Compliant - The Trials of Apollo, Post-The Blood of Olympus (Heroes of Olympus), Season/Series 06, The Author Regrets Nothing
Language: English
Status: Completed
Published: 2019-12-03
Updated: 2019-12-03
Packaged: 2021-02-18 09:03:46
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,457
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/21658408
Author URL: https://archiveofourown.org/users/Josh89/pseuds/Josh89
Summary: Kate and Castle investigate the death of a woman killed by very strange means, and something weird ends up happening
Relationships: Kate Beckett/Richard Castle
Kudos: 7





	The Trail

**Author's Note:**

> So this was originally written as a prompt for a friend who wanted me to write a PJO/Castle crossover. I don't know exactly whether I'll continue this story since she never requested a second chapter, but if there are enough comments asking for it to be continued (or if this gets a ton of hits/kudos) then I might.

-Kate Beckett-  
Broken from a peaceful sleep by the sound of chirping coming from the bedside table on her right, her first thought was to roll over, cuddle closer into her fiancée’s warm embrace, and go back to sleep. Unfortunately, as the chirping grew more and more insistent, she knew that she was not going to get what she wanted anytime soon. She reached out and snatched the offender from her bedside table, putting the device to her ear. “Beckett”.  
She winced inwardly at the harsher tone that her voice had involuntarily taken. “Just wanted to let you know we’ve got a body drop. No need to snap at me, Beckett” the Irish detective answered from the other side of the line.  
She sighed, her voice soft when she responded. “You’re right, Ryan. I’m sorry, it’s just… Castle and I didn’t get back home until late last night. Alexis aced a major college exam, and we had dinner with her to celebrate. Then we went for a walk in the park and didn’t get back until after 10 pm when we went straight to bed. We’re both still exhausted”.  
“I see”.  
Kate nodded, though she knew that the other detective wasn’t going to be able to see it. “Yes. Anyway, you said something about a body drop? Where is it?”  
There was a slight pause from the other side of the line, followed by the rustling of papers. Apparently, the younger detective was trying to find the case notes he’d written down. Kate sighed again. “Text me the location once you’ve sorted everything out. I’m going to wake Castle and then get ready. We’ll meet you there”.  
She swiftly slid her finger across the touch screen of the iPhone that Castle had bought her for her birthday, hanging up before the Irish detective could even respond. Leaning over, she shook her fiancée’s shoulder gently. “Castle… come on, Castle, wake up… We’ve got a case, and if you don’t get up soon, I’ll leave without you…”  
The writer bolted upright in bed almost immediately, his cobalt-blue eyes flickering, disoriented, around the room before finally settling on the face of the detective sitting on the bed beside him. “Kate? What… What time is it?”  
“Almost 5. Come on, we need to get ready and head out. Ryan just called about a body drop”.  
Kate swung her long legs over her side of their queen-sized bed, getting easily to her feet, before heading in the direction of the bathroom.  
~Shortly afterward ~  
Kate pulled the car to a stop and stepped out onto the pavement, waiting a few seconds for her fiancée to join her before beginning to walk briskly towards the entrance to the alleyway where the body had been found. “What have you got for us, Lanie?” she queried.  
The darker-skinned medical examiner glanced up from the body to meet the detective’s hazel eyes. “The victim is a white female, between 23 and 25 years of age. I’d estimate time of death to be between three and four hours ago”.  
Kate handed Rick her coffee and pulled a pair of gloves from her pocket, slipping them onto her hands before crouching down beside her friend, only dimly aware of Castle doing the same thing to the left of her. “Do we have a cause of death yet?” the writer queried, his voice soft.  
Lanie reached out and pulled the collar of the victim’s jacket away from her body, causing both Castle and Beckett to grimace and glance away for a second. “Her throat’s been torn out. I’m going to go ahead and say that that was the cause of death, but I’ll be able to tell for sure one way or the other once I get her back to the morgue”.  
Kate nodded as she and Castle got to their feet. “That’ll do for the time being. Let us know when you find something more concrete”.  
As Lanie nodded, Kate took a sip of her coffee, savoring the sweet liquid as it slid down her throat, and turned to Ryan and Esposito, who were standing a few steps away. “Ask around the apartments on either side of this alleyway. Someone had to have heard or seen something. Castle and I will look around here for a little bit longer and then meet you back at the Precinct”.  
Both detectives nodded in agreement before heading for the exit of the alleyway. They had a killer to catch. It was time to get to work.  
~Ten minutes later~  
A low growl filled the air, breaking the comfortable silence that had formed between Kate and Rick as they searched the alleyway for anything that might lead them to the killer. Kate looked up from where she was kneeling by the wall, glancing over to her fiancée, who was kneeling near where the body had previously laid, looking for anything that might help them solve the case. “Was that your stomach, Castle?” she queried.  
He glanced up, shaking his head. “Not mine, no”.  
-Richard Castle-  
Rick glanced up again only a couple of moments later, only to notice a strange black dog-like creature peering at them around the corner. “Kate... Look”.  
By the time Kate looked up, however, the creature had vanished around the corner. Rick’s fiancée glared at him. “Stop joking around, Rick. This is serious. A woman’s been murdered here!”  
“I am being serious! I saw this black dog-like… thing… staring around the corner at us!” Rick protested defensively.  
“Well, where is it now then?”  
“I don’t know! It vanished around the corner just before you looked up!” he replied.  
Sighing, Kate stood and walked briskly to the road, eyes flicking from side to side as she reached the alleyway, then turned to shake her head at her fiancée. “Are you absolutely sure you weren’t imagining seeing anything, Castle? Neither of us got much sleep last night, perhaps your eyes were playing tricks on you” she said softly, walking back to where her fiancée knelt and crouching down next to him, placing a gentle hand on his shoulder and leaning slightly into his side.  
“I’m as wide awake as you are, Kate, I swear”.  
~Around seven hours later~  
-Kate Beckett-  
“For god’s sake, Rick! If you’re going to keep insisting that you saw some sort of dog-like creature following us, why don’t you just go home already?” Kate snapped exasperatedly.  
The couple had decided to take a detour through Central Park on the way back to the Precinct from their victim’s apartment, and Castle’s eyes had been flickering watchfully from side to side every couple of seconds, ever alert. When her fiancée spoke after a couple of seconds pause, his tone was shaky, panicked, and she could tell that he was genuinely afraid. “Kate… Turn around, but do it slowly. Make no sudden movements”.  
Kate was seconds away from asking her fiancée what the hell he was playing at, when a low growl, a sound eerily similar to the one that they had heard in the alleyway that morning, hit her ears. Tightening her grip on her service weapon, she turned, only to see Castle standing with his back to her, walking backward and away from a black dog the size of a tank. “Shit”.  
“Now do you believe me?” Castle demanded.  
The dog snarled at them, revealing a mouth of vicious-looking teeth. “The hell is that thing, Castle?” Kate hissed.  
“I wish I knew. It looks like a hellhound, but that can’t be right…”  
The creature leaped towards the writer almost as soon as he finished speaking, teeth bared. Kate screamed his name as she raised her handgun to shoot the creature, but she couldn’t get a decent shot without risking hitting Castle as well.  
Just as the dog was about to pounce on the writer, knocking him over, a bronze-tipped arrow struck it in the side, sending it crashing to the ground. “Wrong move, monster!”  
Kate whirled to her right, spotting a black-haired girl striding towards them, a bow in her hand. Her cold blue eyes were fixed on the dog, and her black hair was pinned back. A silver circlet glinted on top of her hair. “Been tracking that hellhound for three damn days now. It’s about time I caught up with it” she muttered.  
The girl drew a knife from her side, plunging it to the hilt in the creature’s chest. Another low growl was heard before the creature simply exploded into golden dust, which vanished instantly upon hitting the ground. The girl gave a satisfied sigh and wiped some of the dust off of her knife before sheathing it again. “Who the hell are you?” Kate demanded.  
“Thalia Grace. And I just saved your boyfriend’s life”.


End file.
